Information about the structure and function of the oral mechanism is believed to be useful in gaining an in-depth understanding of various factors that contribute to a speech production impairment. Clinical evaluations of speech disorders are frequently made by speech professionals, such as clinicians and speech-language pathologists, based upon findings from an oral mechanism examination of the patient. During the examination, various information concerning the performance of the articulators of the patient is collected.
One measure frequently obtained by clinicians during an oral mechanism examination is the strength of the articulatory muscles, particularly the tongue. One of the problems, however, in obtaining reliable tongue strength information is that most strength measurements are made subjectively by the clinician. For example, the patient is frequently asked to press the tongue as hard as possible against a tongue blade. Judgments are then made by the clinician as to the strength of the tongue. Subjective judgments of tongue strength, however, may not always provide consistent or reliable results. For example, subtle weaknesses of the tongue may not be consistently detected, or even detected at all, by subjective tongue strength measurements. In addition, small incremental decreases or increases in tongue strength related to either disease progression or therapy are also sometimes difficult to detect by subjective measures.
Another potential deficiency with routine oral mechanism examinations is that measurements of tongue endurance or fatigability are not generally made. In addition to tongue strength, tongue endurance or fatigue may be an important factor to assess in diagnosing various speech problems or pathological conditions affecting the oral mechanism. For example, rapid fatigue may result in the inability of the patient to maintain accurate articulatory postures during continuous speech. Moreover, changes in fatigue measurements during periodic reassessments may also aid in the evaluation of the progression of a particular disease or the benefit derived from a selected treatment program.
While some instrumentation has been developed to aid in the detection of tongue strength, certain drawbacks still exist. For example, a force transduction system has been employed in which subjects press their tongues against a metal lever to detect the force that can be generated by the tongue. A potential drawback, however, is that the use of the rigid lever may cause patient discomfort thereby adversely affecting a patient's willingness, if not ability, to exert maximum force on the lever with the tongue.
Still other conventional systems have been developed in which a thick-walled, hollow rubber ball is employed in conjunction with a mercury-filled manometer to measure pressure generated by the tongue. This type of system also suffers from drawbacks. For example, the use of a relatively hard rubber ball may not always be suitable to detect relatively small applications of pressure. In addition, the use of a mercury-filled manometer may not be convenient. For example, the system lacks the capability to provide consistent steady readings as well as a convenient output for conducting tongue endurance and fatigability tests.
In accordance with the present invention, a highly efficient and reliable system and method are provided for detecting tongue strength at both maximal and submaximal performance. In addition, fatigability and endurance tests may be conducted with facility.